The present invention relates to a method for forming metal single-layer film, a method for forming wiring, and a method for producing field effect transistors.
Any semiconductor device having an insulating SiO2 film and a gold or platinum layer (for wiring or electrode) formed directly thereon involves difficulty with adhesion between them. A common way to prevent the metal layer from peeling off from the insulating layer is to interpose an adhesion layer of titanium or chromium between them.
The disadvantage of the multi-layer structure having a metal layer and an adhesion layer is that their patterning sometimes present difficulties under some etching conditions. Another disadvantage is an increased production cost due to additional materials and processes, caused by forming the adhesion layer. Moreover, the titanium adhesion layer decreases the channel mobility through the entire transistor (due to charge movement between titanium and channel) in the case of a semiconductor device having a channel-forming region which is in contact with both the source/drain electrodes of gold and the adhesion layer of titanium.